SnO_2添加によるα-Fe_2O_3の還元抑制効果

概要

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Reduction behavior of α-Fe_2O_3 containing SnO_2, Al_2O_3 or Cr_2O_3 under low oxygen pressure(nitrogen atmosphere)was investigated by the thermogravimetry. α-Fe_2O_3 powders mixed with 1-10 mol% SnO_2, 5 mol% Al_2O_3 or 5 mol% Cr_2O_3 were pressed, sintered at 1250℃ for 10h, and then crushed. 5 mol% Al_2O_3 and 5 mol% Cr_2O_3 made solid solutions with α-Fe_2O_3, and SnO_2 was estimated to dissolve up to about 9 mol% at 1250℃ for 10h. Pure α-Fe_2O_3 was reduced between 1150 and 1300℃. The reduction behavior of α-Fe_2O_3 with 5 mol% Al_2O_3 or 5 mol% Cr_2O_3 was similar to that of pure α-Fe_2O_3, and there was no effect of Al_2O_3 or Cr_2O_3 addition on the reduction inhibition of α-Fe_2O_3. On the other hand, the onset temperature and the offset temperature of weight loss for α-Fe_2O_3 with SnO_2 increased with increasing SnO_2 content. The activation energy for the reduction reaction of α-Fe_2O_3 was calculated to be about 633 kJ/mol by Ozawa method, and this value coincides with the activation energy for oxygen diffusion in α-Fe_2O_3. Therefore, it is considered that the reduction reaction of α-Fe_2O_3 was controlled by the oxygen diffusion. The reduction inhibition of α-Fe_2O_3 by SnO_2 addition has been explained by the suppressed creation of oxygen ion defects responsible for oxygen ion diffusion.
社団法人日本セラミックス協会の論文
1998-02-01